//#pragma GCC optimize("Ofast")
//#pragma GCC target("avx,avx2,sse,sse2,sse3,ssse3,sse4,abm,popcnt,mmx")
#include <bits/stdc++.h>
using namespace std;
typedef int ll;
typedef double db;
typedef long double ldb;
typedef complex<double> cd;
constexpr ll INF64 = 9000000000000000000, INF32 = 2000000000, MOD = 1000000007;
constexpr db PI = acos(-1);
constexpr bool IS_FILE = false, IS_TEST_CASES = false;
random_device rd;
mt19937 rnd32(rd());
mt19937_64 rnd64(rd());
template<typename T>
bool assign_max(T& a, T b) {
if (b > a) {
a = b;
return true;
}
return false;
}
template<typename T>
bool assign_min(T& a, T b) {
if (b < a) {
a = b;
return true;
}
return false;
}
template<typename T>
T square(T a) {
return a * a;
}
template<>
struct std::hash<pair<ll, ll>> {
ll operator() (pair<ll, ll> p) {
return ((__int128)p.first * MOD + p.second) % INF64;
}
};
struct segment_tree {
vector<ll> tree;
ll size;
segment_tree(vector<ll> a = vector<ll>(0, 0)) {
size = 1;
while (size < a.size()) {
size *= 2;
}
tree.resize(size * 2, 0);
a.resize(size, 0);
build(1, 0, size, a);
}
ll build(ll v, ll l, ll r, vector<ll>& a) {
if (r - l == 1) {
return tree[v] = a[l];
}
ll mid = (l + r) / 2;
return tree[v] = build(v * 2, l, mid, a) + build(v * 2 + 1, mid, r, a);
}
ll get(ll l, ll r) {
return get(1, 0, size, l, r);
}
ll get(ll v, ll l, ll r, ll ql, ll qr) {
if (ql <= l && r <= qr) {
return tree[v];
}
if (qr <= l || r <= ql) {
return 0;
}
ll mid = (l + r) / 2;
return get(v * 2, l, mid, ql, qr) + get(v * 2 + 1, mid, r, ql, qr);
}
};
void solve() {
ll n;
cin >> n;
vector<ll> pos(n);
for (ll i = 0; i < n; i++) {
ll x;
cin >> x;
x--;
pos[x] = i;
}
vector<segment_tree> all;
for (ll i = 0; i <= n; i++) {
vector<ll> now(n);
for (ll j = 0; j < n; j++) {
now[j] = pos[j] > i;
}
all.emplace_back(now);
}
vector<ll> dp(n, INF32);
dp[0] = 0;
for (ll i = 1; i < n; i++) {
ll now = 0;
for (ll j = i - 1; j >= 0; j--) {
now += all[pos[j + 1]].get(0, j + 1);
//for (ll k = 0; k <= j; k++) {
// if (pos[k] > pos[j + 1]) {
// now++;
// }
//}
ll x = all[pos[j + 1]].get(j + 2, i + 1);
now += x;
now -= (i - j - 1) - x;
//for (ll k = j + 2; k <= i; k++) {
// if (pos[k] > pos[j + 1]) {
// now++;
// } else {
// now--;
// }
//}
assign_min(dp[i], now + dp[j]);
}
now = 0;
for (ll k = 0; k <= i; k++) {
now += k - all[pos[k]].get(0, k);
//for (ll l = 0; l < k; l++) {
// if (pos[k] > pos[l]) {
// now++;
// }
//}
}
assign_min(dp[i], now);
}
cout << dp.back() << '\n';
}
int main() {
if (IS_FILE) {
freopen("", "r", stdin);
freopen("", "w", stdout);
}
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
ll t = 1;
if (IS_TEST_CASES) {
cin >> t;
}
for (ll i = 0; i < t; i++) {
solve();
}
}
